In order to measure a blood sugar level of a patient with diabetes, it is required to take a sample of the blood from the patient. The small amount of the blood to be taken can be enough. Thus, a lancet capable of taking a small amount of blood is used to measure the blood sugar level. The lancet is generally equipped with a pricking needle capable of puncturing a predetermined region of the patient's body (see, for example, U.S. Pat. No. 5,385,571).
In general, the lancet is used in conjunction with an injector. The injector has a function of launching the lancet toward the predetermined region. By loading the lancet into the injector, the pricking device is set up for use. The lancet loaded into the injector is launched toward the predetermined region by means of a plunger of the injector, whereby the predetermined region is pricked.
The present applicant has invented the following pricking device, and filed the application regarding such device (WO 2007/018215 A1, filed date: 8 Aug. 2006, title of the invention: “PRICKING DEVICE, AS WELL AS LANCET ASSEMBLY AND INJECTOR ASSEMBLY THAT CONSTITUTE THE PRICKING DEVICE”). Referring to the accompanying drawings, the lancet assembly and the injector assembly invented by the applicant will be briefly explained below (note that the term “lancet assembly” will be hereinafter referred to also as “lancet”, and the term “injector assembly” will be hereinafter referred to also as “injector”). FIG. 14 shows an external appearance of a lancet 100′, and FIG. 15 shows an external appearance of an injector 200′. As shown in FIGS. 16 and 17, the lancet 100′ is composed of a lancet body 104′, lancet cap 106′ and a pricking component 105′. The pricking component 105′ is attached to the lancet body 104′, and the tip of the pricking needle is covered with the lancet cap 106′. The lancet cap 106′ and the lancet body 104′ are integrally connected together by a weakened part 108′. As shown in FIGS. 14 and 17, the protective cover 102′ is provided to enclose a part of the lancet body 104′. Such lancet 100′ is loaded into the injector 200′, and thereafter the lancet cap 106′ is removed. By the removal of the lancet cap, the tip of the pricking needle 105′ is exposed, and thereby the lancet becomes ready for pricking.
The injector 200′ shown in FIG. 15 can be used in combination with the lancet 100′ to launch the lancet body with the tip of the pricking needle 105′ exposed. The injector 200′ comprises a plunger 204′. The plunger 204′ is capable of engaging with a rear end portion of the lancet body to launch the lancet body in the pricking direction (see FIG. 18). As shown in FIG. 18, the lancet 100′ is loaded into the injector 200′ by inserting the lancet 100′ into the injector 200′ through a front end opening 214′ of the injector 200′. As shown in FIG. 19, when the lancet is inserted to some degree, a rear portion 116′ of the lancet 100′ is held by tips 264′ and 266′ of the plunger 204′. Subsequently, when the insertion of the lancet is continued, the plunger 204′ is thrust backward so that the launching energy is stored. That is, the retraction of the plunger 204′ can compress a spring (not shown) provided in the plunger 204′. This means that, when the compression of the spring is released, the plunger instantly moves forward to launch the lancet. FIG. 20 shows the injector 200′ in the state where the plunger has retracted and the launching energy has been stored therein.
After the loading of the lancet 100′ into the injector 200′ is completed, the lancet cap 106′ is removed to expose the tip of the pricking needle 105′. The removal of the lancet cap 106′ will be described as follows:
As shown in FIGS. 16 and 17, the lancet body 104′ and the lancet cap 106′ are integrally connected together by the weakened part 108′ disposed between the lancet body and the lancet cap. The weakened part 108′ is broken by rotating the lancet body 104′ and the lancet cap 106′ around the pricking needle in the reverse direction to each other (see FIG. 20 in which the rotation of the lancet cap in the direction “G” is shown), whereby the removal of the lancet cap 106′ can be performed.
When the pricking operation is carried out, the front end opening 214′ of the injector 200′ is applied to a predetermined region to be pricked (for example, a finger tip). Subsequently, the press part 542′ of a trigger component 514′ is pushed. See FIG. 21. The pushing of the press part 542′ results in an instantaneous expansion of the compressed spring, and thereby forcing the plunger 204′ to move forwardly to prick the predetermined region with the pricking needle.
With respect to the injector, the tip of the plunge, to which tip the lancet is secured, mostly has a cylindrical portion (see FIG. 22). That is, the lancet is inserted into the cylindrical portion of the plunger, and thereby the lancet is secured to the plunger (see JP H05-285127). The lancet is more or less required to have an exact shape size with respect to the cylindrical portion. The exact shape size of the lancet makes it possible to firmly attach the lancet to the cylindrical portion of the plunger. In other words, if the cylindrical portion of the plunger does not have the exact shape size, the lancet cannot be attached to the plunger, and even if can be attached, the lancet is hard to be detached from the plunger at a point time after the pricking operation.
The lancet is used for the periodical measurement of the blood sugar level. This means that the lancet is used very often and disposable. Thus, it has been desired to keep the disposal amount of the used lancet as low as possible.